Method and device for filtering body fluid

ABSTRACT

Medical devices for filtering fluids flowing through a lumen and a method of forming medical devices. The devices can be used in vascular channels, urinary tracts, biliary ducts and the like, and filter emboli and other debris generated at a treatment site.

[0001] This application is a continuation of application Ser. No.08/748,066, which is a continuation of application Ser. No. 08/272,425,now abandoned.

FIELD OF THE INVENTION

[0002] The present invention generally relates to intravascular devicesfor treating certain medical conditions and, more particularly, providesa method of forming intravascular devices and certain novelintravascular occlusion devices. The devices made in accordance with theinvention are particularly well suited for delivery through a catheteror the like to a remote location in a patient's vascular system or inanalogous vessels within a patient's body.

BACKGROUND OF THE INVENTION

[0003] A wide variety of intravascular devices are used in variousmedical procedures. Certain intravascular devices, such as catheters andguidewires, are generally used simply to deliver fluids or other medicaldevices to specific locations within a patient's body, such as aselective site within the vascular system. Other, frequently morecomplex, devices are used in treating specific conditions, such asdevices used in removing vascular occlusions or for treating septaldefects and the like.

[0004] In certain circumstances, it may be necessary to occlude apatient's vessel, such as to stop blood flow through an artery to atumor or other lesion. Presently, this is commonly accomplished simplyby inserting, e.g. Ivalon particles, a trade name for vascular occlusionparticles, and short sections of coil springs into a vessel at a desiredlocation. These “embolization agents” will eventually become lodged inthe vessel, frequently floating downstream of the site at which they arereleased before blocking the vessel. In part due to the inability toprecisely position the embolization agents, this procedure is oftenlimited in its utility.

[0005] Detachable balloon catheters are also used to block patients'vessels. When using such a catheter, an expandable balloon is carried ona distal end of a catheter. When the catheter is guided to the desiredlocation, the balloon is filled with a fluid until it substantiallyfills the vessel and becomes lodged therein. Resins which will hardeninside the balloon, such as an acrylonitrile, can be employed topermanently fix the size and shape of the balloon. The balloon can thenbe detached from the end of the catheter and left in place.

[0006] Such balloon embolizations are also prone to certain safetyproblems, though. For example, if the balloon is not filled enough, itwill not be firmly fixed in the vessel and may drift downstream withinthe vessel to another location, much like the loose embolization agentsnoted above. In order to avoid this problem, physicians may overfill theballoons; it is not uncommon for balloons to rupture and release theresin into the patient's bloodstream.

[0007] In still other procedures, it may not be necessary to permanentlyocclude a vessel, but it may be necessary to provide a filter or thelike to prevent thrombi from passing a particular location. For example,rotating burrs are used in removing atheroma from the lumen of patients'blood vessels. These burrs can effectively dislodge the atheroma, butthe dislodged material will simply float downstream with the flow ofblood through the vessel unless steps are taken to capture the material.

[0008] Some researchers have proposed various traps or filters forcapturing the particulate matter released or created in such procedures.However, such filters generally have not proven to be exceptionallyeffective in actual use. Such filters tend to be cumbersome to use andaccurate deployment is problematic because if they are not properlyseated in the vessel they can drift to a more distal site where they arelikely to do more harm than good. In addition, these filters aregenerally capable of only trapping relatively large thrombi and are noteffective means for removing smaller embolic particles from the bloodstream.

[0009] The problems with temporary filters, which are intended to beused only during a particular procedure then retracted with the thrombitrapped therein, are more pronounced. Even if the trap does effectivelycapture the dislodged material, it has proven to be relatively difficultor complex to retract the trap back into the catheter through which itwas delivered without simply dumping the trapped thrombi back into theblood stream, defeating the purpose of the temporary filter device. Forthis reason, most atherectomy devices and the like tend to aspirate thepatient's blood during the procedure to remove the dislodged materialentrained therein.

[0010] Mechanical embolization devices, filters and traps have beenproposed in the past. Even if some of those devices have proveneffective, they tend to be rather expensive and time-consuming tomanufacture. For example, some intravascular blood filters suggested byothers are formed of a plurality of specially-shaped legs which areadapted to fill the vessel and dig into the vessel walls. In making mostsuch filters, the legs must be individually formed and thenpainstakingly attached to one another, frequently entirely by hand, toassemble the final filter. Not only does this take significant skilledmanpower, and hence increase the costs of such devices, the fact thateach item must be made by hand tends to make quality control moredifficult. This same difficulty and expense of manufacturing is notlimited to such filters, but is experienced in many other intravasculardevices as well.

[0011] Accordingly, it would be desirable to provide a method forforming devices for deployment in a vessel in a patient's vessel whichis both economical and yields consistent, reproducible results. It wouldalso be advantageous to provide a reliable embolization device which isboth easy to deploy and can be accurately placed in a vessel.Furthermore, there is a need in the art for a trap or filter which canbe deployed within a vessel for capturing thrombi, which trap can bereliably deployed; if the trap is to be used only temporarily, it shouldbe readily withdrawn from the patient without simply dumping the trappedthrombi back into the blood stream.

SUMMARY OF THE INVENTION

[0012] The present invention provides a method for forming intravasculardevices from a resilient metal fabric and medical devices which can beformed in accordance with this method. In the method of the invention, ametal fabric formed of a plurality of resilient strands is provided,with the wires being formed of a resilient material which can be heattreated to substantially set a desired shape. This fabric is thendeformed to generally conform to a molding surface of a molding elementand the fabric is heat treated in contact with the surface of themolding element at an elevated temperature. The time and temperature ofthe heat treatment is selected to substantially set the fabric in itsdeformed state. After the heat treatment, the fabric is removed fromcontact with the molding element and will substantially retain its shapein the deformed state. The fabric so treated defines an expanded stateof a medical device which can be deployed through a catheter into achannel in a patient's body.

[0013] In accordance with the method of the invention, a distal end of acatheter can be positioned in a channel in a patient's body to positionthe distal end of the catheter adjacent a treatment site for treating aphysiological condition. A medical device made in accordance with theprocess outlined above can be collapsed and inserted into the lumen ofthe catheter. The device is urged through the catheter and out thedistal end, whereupon it will tend to return to its expanded stateadjacent the treatment site.

[0014] Further embodiments of the present invention also providespecific medical devices which may be made in accordance with thepresent invention. Such devices of the invention are formed of a metalfabric and have an expanded configuration and a collapsed configuration.The devices are collapsed for deployment through a catheter and, uponexiting the distal end of the catheter in a patient's channel, willresiliently substantially return to their expanded configuration. Inaccordance with a first of these embodiments, a generally elongatemedical device has a generally tubular middle portion and a pair ofexpanded diameter portions, with one expanded diameter portionpositioned at either end of the middle portion. In another embodiment,the medical device is generally bell-shaped, having an elongate bodyhaving a tapered first end and a larger second end, the second endpresenting a fabric disc which will be oriented generally perpendicularto an axis of a channel when deployed therein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIGS. 1A and 1B each depict a metal fabric suitable for use withthe invention;

[0016]FIGS. 2A and 2B are a side view and a perspective view,respectively, of a molding element and a length of a metal fabricsuitable for use in forming a medical device in accordance with theinvention, the mold being in a disassembled state;

[0017]FIG. 3A is a perspective view showing the molding element andmetal fabric of FIG. 2 in a partially assembled state;

[0018]FIG. 3B is a close-up view of the highlighted area of FIG. 3Ashowing the compression of the metal fabric in the molding element;

[0019]FIG. 4 is a cross-sectional view showing the molding element andmetal fabric of FIG. 2 in an assembled state;

[0020]FIGS. 5A and 5B are a side view and an end view, respectively, ofa medical device in accordance with the invention;

[0021] FIGS. 6A-6C are a side view, an end view and a perspective view,respectively, of a medical device in accordance with another embodimentof the invention;

[0022]FIG. 7 is a side, cross sectional view of a molding elementsuitable for forming the medical device shown in FIGS. 6A-6C;

[0023]FIG. 8 is a schematic illustration showing the device of FIGS.6A-6C deployed in a channel of a patient's vascular system to occlude aPatent Ductus Arteriosus;

[0024]FIGS. 9A and 9B are a side view and an end view, respectively, ofa medical device in accordance with yet another embodiment of theinvention;

[0025]FIG. 10A is a side view of one molding element suitable forforming the invention of FIGS. 9A and 9B;

[0026]FIG. 10B is a cross-sectional view of another molding elementsuitable for forming the invention of FIGS. 9A and 9B;

[0027]FIG. 10C is a cross-sectional view of still another moldingelement suitable for forming the invention of FIGS. 9A and 9B;

[0028]FIG. 11A is a schematic side view of yet another medical devicemade in accordance with the invention showing the device in a collapsedstate for deployment in a patient's vascular system;

[0029]FIG. 11B is a schematic side view of the medical device of FIG.11A in an expanded state for deployment in a patient's vascular system;

[0030]FIG. 12A is a schematic side view of an alternative embodiment ofthe invention of FIG. 11A showing the device in a collapsed state withincatheter for deployment;

[0031]FIG. 12B is a schematic side view of the device of FIG. 12Ashowing the device deployed distally of the catheter;

[0032]FIG. 13 is a schematic perspective view showing a medical devicein accordance with yet a further embodiment of the invention collapsedwithin a catheter for deployment in a channel in a patient's body;

[0033]FIG. 14 is a schematic side view of the device of FIG. 13 in apartially deployed state; and

[0034]FIG. 15 is a schematic side view of the device of FIG. 13 in afully deployed state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] The present invention provides a reproducible, relativelyinexpensive method of forming devices for use in channels in patients'bodies, such as vascular channels, urinary tracts, biliary ducts and thelike, as well as devices which may be made via that method. In forming amedical device via the method of the invention, a metal fabric 10 isprovided. The fabric is formed of a plurality of wire strands having apredetermined relative orientation between the strands. FIGS. 1A and 1Billustrate two examples of metal fabrics which are suitable for use inthe method of the invention.

[0036] In the fabric of FIG. 1A, the metal strands define two sets ofessentially parallel generally helical strands, with the strands of oneset having a “hand”, i.e. a direction of rotation, opposite that of theother set. This defines a generally tubular fabric, known in the fabricindustry as a tubular braid. Such tubular braids are well known in thefabric arts and find some applications in the medical device field astubular fabrics, such as in reinforcing the wall of a guiding catheter.As such braids are well known, they need not be discussed at lengthhere. The pitch of the wire strands (i.e. the angle defined between theturns of the wire and the axis of the braid) and the pick of the fabric(i.e. the number of turns per unit length) may be adjusted as desiredfor a particular application. For example, if the medical device to beformed is to be used to occlude the channel in which it is placed, thepitch and pick of the fabric will tend to be higher than if the deviceis simply intended to filter bodily fluid passing therethrough.

[0037] For example, in using a tubular braid such as that shown in FIG.1A to form a device such as that illustrated in FIGS. 5A and 5B, atubular braid of about 4 mm in diameter with a pitch of about 50° and apick of about 74 (per linear inch) would seem suitable for a devicesused in occluding channels on the order of about 2 mm to about 4 mm ininner diameter, as detailed below in connection with the embodiment ofFIGS. 5A and 5B.

[0038]FIG. 1B illustrates another type of fabric which is suitable foruse in the method of the invention. This fabric is a more conventionalfabric and may take the form of a flat woven sheet, knitted sheet or thelike. In the woven fabric shown in FIG. 1B, there are also two sets 14and 14′ of generally parallel strands, with one set of strands beingoriented at an angle, e.g. generally perpendicular (having a pick ofabout 90°), with respect to the other set. As noted above, the pitch andpick of this fabric (or, in the case of a knit fabric, the pick and thepattern of the knit, e.g. Jersey or double knits) may be selected tooptimize the desired properties of the final medical device.

[0039] The wire strands of the metal fabric used in the present methodshould be formed of a material which is both resilient and can be heattreated to substantially set a desired shape. Materials which arebelieved to be suitable for this purpose include a cobalt-based lowthermal expansion alloy referred to in the field as Elgiloy, nickelbased high-temperature high-strength “superalloys” commerciallyavailable from Haynes International under the trade name Hastelloy,nickel-based heat treatable alloys sold under the name Incoloy byInternational Nickel, and a number of different grades of stainlesssteel. The important factor in choosing a suitable material for thewires is that the wires retain a suitable amount of the deformationinduced by the molding surface (as described below) when subjected to apredetermined heat treatment.

[0040] One class of materials which meet these qualifications areso-called shape memory alloys. Such alloys tend to have a temperatureinduced phase change which will cause the material to have a preferredconfiguration which can be fixed by heating the material above a certaintransition temperature to induce a change in the phase of the material.When the alloy is cooled back down, the alloy will “remember” the shapeit was in during the heat treatment and will tend to assume thatconfiguration unless constrained from so doing.

[0041] One particularly preferred shape memory alloy for use in thepresent method is nitinol, an approximately stoichiometric alloy ofnickel and titanium, which may also include other minor amounts of othermetals to achieve desired properties. NiTi alloys such as nitinol,including appropriate compositions and handling requirements, are wellknown in the art and such alloys need not be discussed in detail here.For example, U.S. Pat. Nos. 5,067,489 (Lind) and 4,991,602 (Amplatz etal.), the teachings of which are incorporated herein by reference,discuss the use of shape memory NiTi alloys in guidewires. Such NiTialloys are preferred, at least in part, because they are commerciallyavailable and more is known about handling such alloys than other knownshape memory alloys. NiTi alloys are also very elastic—they are said tobe “superelastic” or “pseudoelastic”. This elasticity will help a deviceof the invention return to a present expanded configuration fordeployment.

[0042] The wire strands can comprise a standard monofilament of theselected material, i.e. a standard wire stock may be used. If sodesired, though, the individual wire strands may be formed from “cables”made up of a plurality of individual wires. For example, cables formedof metal wires where several wires are helically wrapped about a centralwire are commercially available and NiTi cables having an outer diameterof 0.003 inches or less can be purchased. One advantage of certaincables is that they tend to be “softer” than monofilament wires havingthe same diameter and formed of the same material. Additionally, if thedevice being formed from the wire strands is to be used to occlude avessel, the use of a cable can increase the effective surface area ofthe wire strand, which will tend to promote thrombosis.

[0043] In preparation of forming a medical device in keeping with theinvention, an appropriately sized piece of the metal fabric is cut fromthe larger piece of fabric which is formed, for example, by braidingwire strands to form a long tubular braid. The dimensions of the pieceof fabric to be cut will depend, in large part, upon the size and shapeof the medical device to be formed therefrom.

[0044] When cutting the fabric to the desired dimensions, care should betaken to ensure that the fabric will not unravel. In the case of tubularbraids formed of NiTi alloys, for example, the individual wire strandswill tend to return to their heat-set configuration unless constrained.If the braid is heat treated to set the strands in the braidedconfiguration, they will tend to remain in the braided form and only theends will become frayed. However, it may be more economical to simplyform the braid without heat treating the braid since the fabric will beheat treated again in forming the medical device, as noted below.

[0045] In such untreated NiTi fabrics, the strands will tend to returnto their unbraided configuration and the braid can unravel fairlyquickly unless the ends of the length of braid cut to form the deviceare constrained relative to one another. One method which has proven tobe useful to prevent the braid from unraveling is to clamp the braid attwo locations and cut the braid to leave a length of the braid havingclamps (15 in FIG. 2) at either end, thereby effectively defining anempty space within a sealed length of fabric. These clamps 15 will holdthe ends of the cut braid together and prevent the braid fromunraveling.

[0046] Alternatively, one can solder, braze, weld or otherwise affix theends of the desired length together (e.g. with a biocompatiblecementitious organic material) before cutting the braid. Althoughsoldering and brazing of NiTi alloys has proven to be fairly difficult,the ends can be welded together, such as by spot welding with a laserwelder.

[0047] The same problems present themselves when a flat sheet of fabricsuch as the woven fabric shown in FIG. 1B is used. With such a fabric,the fabric can be inverted upon itself to form a recess or depressionand the fabric can be clamped about this recess to form an empty pocket(not shown) before the fabric is cut. If it is desired to keep thefabric in a generally flat configuration, it may be necessary to weldthe junctions of the strands together adjacent the periphery of thedesired piece of fabric before that piece is cut from the larger sheet.So connecting the ends of the strands together will prevent fabricsformed of untreated shape memory alloys and the like from unravelingduring the forming process.

[0048] Once an appropriately sized piece of the metal fabric isobtained, the fabric is deformed to generally conform to a surface of amolding element. As will be appreciated more fully from the discussionbelow in connection with FIGS. 2-16, so deforming the fabric willreorient the relative positions of the strands of the metal fabric fromtheir initial order to a second, reoriented configuration. The shape ofthe molding element should be selected to deform the fabric intosubstantially the shape of the desired medical device.

[0049] The molding element can be a single piece, or it can be formed ofa series of mold pieces which together define the surface to which thefabric will generally conform. The molding element can be positionedwithin a space enclosed by the fabric or can be external of such aspace, or can even be both inside and outside such a space.

[0050] In order to illustrate one example of how such a mold may beconfigured and how it may be used in accordance with the method of theinvention, reference will be had to FIGS. 2-5. In FIGS. 2-4, the moldingelement 20 is formed of a number of separate pieces which can beattached to one another to complete the molding element 20. In usingsuch a multi-piece molding element, the mold can be assembled about thecut length of fabric 10, thereby deforming the fabric to generallyconform to the desired surface (or surfaces) of the molding element.

[0051] In the molding element illustrated in FIGS. 2-4, the metal fabric10 is deformed to generally conform to a surface of the molding element20, the molding element comprising a center section 30 and a pair of endplates 40. Turning first to the center section 30, the center section isdesirably formed of opposed halves 32, 32 which can be moved away fromone another in order to introduce the metal fabric 10 into the mold.Although these two halves 32, 32 are shown in the drawings as beingcompletely separated from one another, it is to be understood that thesehalves could be interconnected, such as by means of a hinge or the like,if so desired. The opposed halves of the molding element 20 shown in thedrawings of FIGS. 2 and 3 each include a pair of semi-circular recessesopposed on either side of a ridge defining a generally semi-circularopening. When the two halves are assembled in forming the device, asbest seen in FIG. 3, the semi-circular openings in the opposed halves32, 32 mate to define a generally circular forming port 36 passingthrough the center section 30. Similarly, the semi-circular recesses inthe two halves together form a pair of generally circular centralrecesses 34, with one such recess being disposed on either face of thecenter section.

[0052] The overall shape and dimensions of the center section can bevaried as desired; it is generally the size of the central recesses 34and the forming port 36 which will define the size and shape of themiddle of the finished device, as explained below. If so desired, eachhalf 32 may be provided with a manually graspable projection 38. In theembodiment shown in the drawings, this projection 38 is provided at alocation disposed away from the abutting faces of the respective halves.Such a manually graspable projection 38 will simply enable an operatorto more easily join the two halves to define the recesses 34 and formingport 36.

[0053] The center section is adapted to cooperatively engage a pair ofend plates 40 for forming the desired device. In the embodiment shown inFIGS. 2 and 3, the center section 30 has a pair of flat outer faces 39which are each adapted to be engaged by an inner face 42 of one of thetwo end plates 40. Each end plate includes a compression disk 44 whichextends generally laterally inwardly from the inner face 42 of the endplate. This compression disk 44 should be sized to permit it to bereceived within one of the central recesses 34 on either face of thecenter section 30. For reasons explained more fully below, eachcompression disk 44 includes a cavity 46 for receiving an end of thelength of the metal fabric 10.

[0054] One or more channels 48 for receiving bolts and the like may alsobe provided through each of the end plates and through the centersection 30. By passing bolts through these channels 48, one can assemblethe molding element 20 and retain the metal fabric in the desired shapeduring the heat treatment process, as outlined below.

[0055] In utilizing the molding element 20 shown in FIGS. 2-4, a lengthof the metal fabric 10 can be positioned between the opposed halves 32of the center section 30. In the drawings of the molding element 20 ofFIGS. 2-4, the metal fabric 10 is a tubular braid such as thatillustrated in FIG. 1A. A sufficient length of the tubular braid shouldbe provided to permit the fabric to conform to the molding surface, asexplained below. Also, as noted above, care should be taken to securethe ends of the wire strands defining the tubular braid in order toprevent the metal fabric from unraveling.

[0056] A central portion of the length of the metal braid may bepositioned within one of the two halves of the forming port 36 and theopposed halves 32 of the center section may be joined to abut oneanother to restrain a central portion of the metal braid within thecentral forming port 36 through the center section.

[0057] The tubular braid will tend to have a natural, relaxed diameterwhich is defined, in large part, when the tubular braid is formed.Unless the tubular braid is otherwise deformed, when the wire strandsare in their relaxed state they will tend to define a generally hollowtube having the predetermined diameter. The outer diameter of therelaxed braid may be, for example, about 4 mm. The relative size of theforming port 36 in the central section 30 of the molding element and thenatural, relaxed outer diameter of the tubular braid may be varied asdesired to achieve the desired shape of the medical device being formed.

[0058] In the embodiment shown in FIGS. 2 and 3, the inner diameter ofthe forming port 36 is optimally slightly less than the natural, relaxedouter diameter of the tubular braid 10. Hence, when the two halves 32,32 are assembled to form the center section 30, the tubular braid 10will be slightly compressed within the forming port 36. This will helpensure that the tubular braid conforms to the inner surface of theforming port 36, which defines a portion of the molding surface of themolding element 20.

[0059] If so desired, a generally cylindrical internal molding section(not shown) may also be provided. This internal molding section has aslightly smaller diameter than the inner diameter of the forming port36. In use, the internal molding section is placed within the length ofthe metal fabric, such as by manually moving the wire strands of thefabric apart to form an opening through which the internal moldingsection can be passed. This internal molding section should bepositioned within the tubular braid at a location where it will bedisposed within the forming port 36 of the center section when themolding element is assembled. There should be a sufficient space betweenthe outer surface of the interior molding section and the inner surfaceof the forming port 36 to permit the wire strands of the fabric 10 to bereceived therebetween.

[0060] By using such an internal molding section, the dimensions of thecentral portion of the finished medical device can be fairly accuratelycontrolled. Such an internal molding section may be necessary incircumstances where the natural, relaxed outer diameter of the tubularbraid 10 is less than the inner diameter of the forming port 36 toensure that the braid conforms to the inner surface of that formingport. However, it is not believed that such an internal molding sectionwould be necessary if the natural, relaxed outer diameter of the braidwere larger than the inner diameter of the forming port 36.

[0061] As noted above, the ends of the tubular braid should be securedin order to prevent the braid from unraveling. Each end of the metalfabric 10 is desirably received within a cavity 46 formed in one of thetwo end plates 40. If a clamp (15 in FIG. 2) is used, the clamp may besized to be relatively snugly received within one of these cavities 46in order to effectively attach the end of the fabric to the end plate40. The end plates can then be urged toward the center section 30 andtoward one another until the compression disk 44 of each end plate isreceived within a central recess 34 of the center section 30. Themolding element may then be clamped in position by passing bolts or thelike through the channels 48 in the molding element and locking thevarious components of the molding element together by tightening a nutdown onto such a bolt (not shown).

[0062] As best seen in FIG. 3A, when an end plate is urged toward thecenter section 30, this will compress the tubular braid 10 generallyalong its axis. When the tubular braid is in its relaxed configuration,as illustrated in FIG. 1A, the wire strands forming the tubular braidwill have a first, predetermined relative orientation with respect toone another. As the tubular braid is compressed along its axis, thefabric will tend to flare out away from the axis, as illustrated in FIG.4. When the fabric is so deformed, the relative orientation of the wirestrands of the metal fabric will change. When the molding element isfinally assembled, the metal fabric will generally conform to themolding surface of this element.

[0063] In the molding element 20 shown in FIGS. 2-4, the molding surfaceis defined by the inner surface of the forming port, the inner surfacesof the central recess 34 and the faces of the compression disks 44 whichare received within the recesses 34. If an internal molding section isused, the cylindrical outer surface of that section may also beconsidered a part of the molding surface of the molding element 20.Accordingly, when the molding element 20 is completely assembled themetal fabric will tend to assume a somewhat “dumbbell”-shapedconfiguration, with a relatively narrow center section disposed betweena pair of bulbous, perhaps even disk-shaped end sections, as best seenin FIG. 4.

[0064] It should be understood that the specific shape of the particularmolding element 20 shown in FIGS. 2-4 is intended to produce one usefulmedical device in accordance with the present method, but that othermolding elements having different configurations could also be used. Ifa more complex shape is desired, the molding element may have moreparts, but if a simpler shape is being formed the molding element mayhave even fewer parts. The number of parts in a given molding elementand the shapes of those parts will be dictated almost entirely by theshape of the desired medical device as the molding element must define amolding surface to which the metal fabric will generally conform.

[0065] Accordingly, the specific molding element 20 shown in FIGS. 2-4is simply intended as one specific example of a suitable molding elementfor forming one particular useful medical device. Additional moldingelements having different designs for producing different medicaldevices are explained below in connection with, e.g., FIGS. 8 and 10.Depending on the desired shape of the medical device being formed, theshape and configuration of other specific molding elements can bereadily designed by those of ordinary skill in the art.

[0066] Once the molding element 20 is assembled with the metal fabricgenerally conforming to a molding surface of that element, the fabriccan be subjected to a heat treatment while it remains in contact withthat molding surface. This heat treatment will depend in large part uponthe material of which the wire strands of the metal fabric are formed,but the time and temperature of the heat treatment should be selected tosubstantially set the fabric in its deformed state, i.e., wherein thewire strands are in their reoriented relative configuration and thefabric generally conforms to the molding surface.

[0067] The time and temperature of the heat treatment can vary greatlydepending upon the material used in forming the wire strands. As notedabove, one preferred class of materials for forming the wire strands areshape memory alloys, with nitinol, a nickel titanium alloy, beingparticularly preferred. If nitinol is used in making the wire strands ofthe fabric, the wire strands will tend to be very elastic when the metalis in its austenitic phase; this very elastic phase is frequentlyreferred to as a “superelastic” or “pseudoelastic” phase. By heating thenitinol above a certain phase transition temperature, the crystalstructure of the nitinol metal when in its austenitic phase can be set.This will tend to “set” the shape of the fabric and the relativeconfiguration of the wire strands in the positions in which they areheld during the heat treatment.

[0068] Suitable heat treatments of nitinol wire to set a desired shapeare well known in the art. Spirally wound nitinol coils, for example,are used in a number of medical applications, such as in forming thecoils commonly carried around distal lengths of guidewires. A wide bodyof knowledge exists for forming nitinol in such medical devices, sothere is no need to go into great detail here on the parameters of aheat treatment for the nitinol fabric preferred for use in the presentinvention.

[0069] Briefly, though, it has been found that holding a nitinol fabricat about 500° C. to about 550° C. for a period of about 1 to about 30minutes, depending on the softness or hardness of the device to be made,will tend to set the fabric in its deformed state, i.e. wherein itconforms to the molding surface of the molding element. At lowertemperatures the heat treatment time will tend to be greater (e.g. aboutone hour at about 350° C.) and at higher temperatures the time will tendto be shorter (e.g. about 30 seconds at about 900° C.). These parameterscan be varied as necessary to accommodate variations in the exactcomposition of the nitinol, prior heat treatment of the nitinol, thedesired properties of the nitinol in the finished article, and otherfactors which will be well known to those skilled in this field.

[0070] Instead of relying on convection heating or the like, it is alsoknown in the art to apply an electrical current to the nitinol to heatit. In the present invention, this can be accomplished by, for example,hooking electrodes to the clamps 15 carried at either end of the metalfabric illustrated in FIG. 2. The wire can then be heated by resistanceheating of the wires in order to achieve the desired heat treatment,which will tend to eliminate the need to heat the entire molding elementto the desired heat treating temperature in order to heat the metalfabric to the desired temperature.

[0071] After the heat treatment, the fabric is removed from contact withthe molding element and will substantially retain its shape in adeformed state. When the molding element 20 illustrated in FIGS. 2-4 isused, the bolts (not shown) may be removed and the various parts of themolding element may be disassembled in essentially the reverse of theprocess of assembling the molding element. If an internal moldingsection is used, this molding section can be removed in much the samefashion that it is placed within the generally tubular metal fabric inassembling the molding element 20, as detailed above.

[0072]FIGS. 5A and 5B illustrate one embodiment of a medical device 60which may be made using the molding element 20 of FIGS. 2-4. Asdiscussed below, the device of FIG. 5 is particularly well suited foruse in occluding a channel within a patient's body and these designshave particular advantages in use as vascular occlusion devices.

[0073] The vascular occlusion device 60 of FIG. 5A includes a generallytubular middle portion 62 and a pair of expanded diameter portions 64.One expanded diameter portion is disposed at either end of the generallytubular middle portion 62. In the embodiment shown in FIGS. 5A and 5B,the expanded diameter portions 64 include a ridge 66 positioned aboutmidway along their lengths.

[0074] The relative sizes of the tubular middle section and the expandeddiameter portions can be varied as desired. In this particularembodiment, the medical device is intended to be used as a vascularocclusion device to substantially stop the flow of blood through apatient's blood vessel. When the device 60 is deployed within apatient's blood vessel, as detailed below, it will be positioned withinthe vessel such that its axis generally coincides with the axis of thevessel. The dumbbell-shape of the present device is intended to limitthe ability of the vascular occlusion device 60 to turn at an angle withrespect to the axis of the blood vessel to ensure that it remains insubstantially the same position in which the operator deploys it withinthe vessel.

[0075] Although the illustrated embodiments of this invention only havetwo expanded diameter portions, it should be understood that the devicecould have more than two such expanded diameter portions. For example,if the device has three expanded diameter portions, each expandeddiameter portion is separated from at least one other expanded diameterportion by a tubular portion having a smaller diameter. If so desired,the diameters of each of the expanded diameter portions can be the samebut they need not be the same.

[0076] In order to relatively strongly engage the lumen of the bloodvessel, the maximum diameter of the expanded diameter portions 64 (whichoccurs along the middle ridge 66 in this embodiment) should be selectedso that it is at least as great as the diameter of the lumen of thevessel in which it is to be deployed, and is optimally slightly greaterthan that diameter. When it is deployed within the patient's vessel, thevascular occlusion device 60 will engage the lumen at two spaced-apartlocations. The device 60 is desirably longer along its axis than thedimension of its greatest diameter. This will substantially prevent thevascular occlusion device 60 from turning within the lumen at an angleto its axis, essentially preventing the device from becoming dislodgedand tumbling along the vessel with blood flowing through the vessel.

[0077] The relative sizes of the generally tubular middle portion 62 andexpanded diameter portion 64 of the vascular occlusion device 60 can bevaried as desired for any particular application. For example, the outerdiameter of the middle portion 62 may range between about one quarterand about one third of the maximum diameter of the expanded diameterportions 64 and the length of the middle portion 62 may comprise about20% to about 50% of the overall length of the device. Although thesedimensions are suitable if the device 60 is to be used solely foroccluding a vascular vessel, it is to be understood that thesedimensions may be varied if the device is to be used in otherapplications, such as where the device is intended to be used simply asa vascular filter rather than to substantially occlude the entire vesselor where the device is deployed in a different channel in a patient'sbody.

[0078] The aspect ratio (i.e., the ratio of the length of the deviceover its maximum diameter or width) of the device 60 illustrated inFIGS. 5A and 5B is desirably at least about 1.0, with a range of about1.0 to about 3.0 being preferred and an aspect ratio of about 2.0 beingparticularly preferred. Having a greater aspect ration will tend toprevent the device from rotating generally perpendicularly to its axis,which may be referred to as an end over end roll. So long as the outerdiameter of the expanded diameter portions 64 of the device is largeenough to seat the device fairly securely against the lumen of thechannel in which the device is deployed, the inability of the device toturn end over end will help keep the device deployed precisely where itis positioned within the patient's vascular system or in any otherchannel in the patient's body. Alternatively, having expanded diameterportions which have natural, relaxed diameters substantially larger thanthe lumen of the vessels in which the device is deployed should alsosuffice to wedge the device into place in the vessel without undueconcern being placed on the aspect ratio of the device.

[0079] The pick and pitch of the metal fabric 10 used in forming thedevice 60, as well as some other factors such as the number of wiresemployed in a tubular braid, are important in determining a number ofthe properties of the device. For example, the greater the pick andpitch of the fabric, and hence the greater the density of the wirestrands in the fabric, the stiffer the device will be. Having a greaterwire density will also provide the device with a greater wire surfacearea, which will generally enhance the tendency of the device to occludea blood vessel in which it is deployed. This thrombogenicity can beeither enhanced, e.g. by a coating of a thrombolytic agent or byattaching silk or wool fabric to the device, or abated, e.g. by acoating of a lubricious, anti-thrombogenic compound. A variety ofmaterials and techniques for enhancing or reducing thrombogenicity arewell known in the art and need not be detailed here.

[0080] When the device is deployed in a patient's vessel, thrombi willtend to collect on the surface of the wires. By having a greater wiredensity, the total surface area of the wires will be increased,increasing the thrombolytic activity of the device and permitting it torelatively rapidly occlude the vessel in which it is deployed. It isbelieved that forming the occlusion device 60 from a 4 mm diametertubular braid having a pick of at least about 40 and a pitch of at leastabout 30° will provide sufficient surface area to substantiallycompletely occlude a blood vessel of 2 mm to about 4 mm in innerdiameter in a suitable period of time. If it is desired to increase therate at which the device 60 occludes the vessel in which it is deployed,any of a wide variety of known thrombolytic agents can be applied to thedevice.

[0081] FIGS. 6A-6C illustrate an alternative embodiment of a medicaldevice in accordance with the present invention. This device 80 has agenerally bell-shaped body 82 and an outwardly extending forward end 84.One application for which this device is particularly well suited isoccluding defects known in the art as patent ductus arteriosus (PDA).PDA is essentially a condition wherein two blood vessels, most commonlythe aorta and pulmonary artery adjacent the heart, have a shunt betweentheir lumens. Blood can flow directly between these two blood vesselsthrough the shunt, compromising the normal flow of blood through thepatient's vessels.

[0082] As explained more fully below in connection with FIG. 8, thebell-shaped body 82 is adapted to be deployed within the shunt betweenthe vessels, while the forward end 84 is adapted to be positioned withinone of the two vessels to help seat the body in the shunt. The sizes ofthe body 82 and the end 84 can be varied as desired for differentlysized shunts. For example, the body may have a diameter along itsgenerally cylindrical middle 86 of about 10 mm and a length along itsaxis of about 25 mm. In such a device, the base 88 of the body may flaregenerally radially outward until it reaches an outer diameter equal tothat of the forward end 84, which may be on the order of about 20 mm indiameter.

[0083] The base 88 desirably flares out relatively rapidly to define ashoulder tapering radially outwardly from the middle 86 of the body.When the device is deployed in a vessel, this shoulder will abut thelumen of one of the vessels being treated. The forward end 84 isretained within the vessel and urges the base 88 of the body open toensure that the shoulder engages the wall of the vessel to prevent thedevice 80 from becoming dislodged from within the shunt.

[0084] As detailed above, in making a device of the invention it isdesirable to attach the ends of the wire strands forming the metalfabric 10 to one another to prevent the fabric from unraveling. In theillustrations of FIGS. 6A-6C, a clamp 15 is used to tie together theends of the wire strands adjacent the front end 84 of the device. It isto be understood that this clamp 15 is simply a schematic illustration,though, and that the ends could be attached in other ways, such as bywelding, soldering, brazing, use of a biocompatible cementitiousmaterial or in any other suitable fashion.

[0085] The rearward ends of the wire strands are shown as being attachedto one another by an alternative clamping means 90. This clamp 90 servesthe same purpose as the schematically illustrated clamp 15, namely tointerconnect the ends of the wires. However the clamp 90 also serves toconnect the device 80 to a delivery system (not shown). In theembodiment shown, the clamp 90 is generally cylindrical in shape and hasa recess for receiving the ends of the wires to substantially preventthe wires from moving relative to one another, and a threaded outersurface. The threaded outer surface is adapted to be received within acylindrical recess (not shown) on a distal end of a delivery device andto engage the threaded inner surface of the delivery device's recess.

[0086] The delivery device (not shown) can take any suitable shape, butdesirably comprises an elongate, flexible metal shaft having such arecess at its distal end. The delivery device can be used to urge thePDA occlusion device 80 through the lumen of a catheter for deploymentin a channel of the patient's body, as outlined below. When the deviceis deployed out the distal end of the catheter, the device will still beretained by the delivery device. Once the proper position of the device80 in the shunt is confirmed, the shaft of the delivery device can berotated about its axis to unscrew the clamp 90 from the recess in thedelivery means.

[0087] By keeping the PDA device 80 attached to the delivery means, theoperator could still retract the device for repositioning if it isdetermined that the device is not properly positioned in the firstattempt. This threaded attachment will also allow the operator tocontrol the manner in which the device 80 is deployed out of the distalend of the catheter. As explained below, when the device exits thecatheter it will tend to resiliently return to a preferred expandedshape which is set when the fabric is heat treated. When the devicesprings back into this shape, it may tend to act against the distal endof the catheter, effectively urging itself forward beyond the end of thecatheter. This spring action could conceivably result in improperpositioning of the device if the location of the device within a channelis critical, such as where it is being positioned in a shunt between twovessels. Since the threaded clamp 90 can enable the operator to maintaina hold on the device during deployment, the spring action of the devicecan be controlled and the operator can control the deployment to ensureproper positioning.

[0088] A PDA occlusion device 80 of this embodiment of the invention canadvantageously be made in accordance with the method outlined above,namely deforming a metal fabric to generally conform to a moldingsurface of a molding element and heat treating the fabric tosubstantially set the fabric in its deformed state. FIG. 7 shows amolding element 100 which may be suitable for forming a PDA occlusiondevice 80 such as that shown in FIGS. 6A-6C.

[0089] The molding element 100 generally comprises a body portion 110and an end plate 120. The body portion 110 is adapted to receive andform the body 82 of the device 80 while the end plate is adapted tocompress against the metal fabric to form the forward end 84. The bodyportion 110 includes an elongate, generally tubular central segment 112which is sized to receive the elongate body 82 of the device. Thecentral segment 112 of the molding element 100 optimally has an internaldiameter slightly less than the natural, relaxed outer diameter of thetubular braid of which the device is formed. This compression of thebraid will help yield devices with reproducibly sized bodies 82. Theforward end of the body portion 110 includes a back plate 114 which hasa generally annular sidewall 116 depending downwardly therefrom. Thesidewall defines a recess 118 which is generally circular in shape.

[0090] The end plate 120 of the molding element 100 has a generallydisc-shaped face 122, which desirably has a clamp port 124 approximatelycentered therein for receiving a clamp 15 attached to the metal fabric,as noted above. The end plate also has an annular sidewall 126 whichextends generally upwardly from the face 122 to define a generallycylindrical recess 128 in the end plate 120. The sidewall 116 of thebody portion 110 is sized to be received within the recess 128 of theend plate.

[0091] In use, the metal fabric is placed in the molding element and thebody portion 110 and the end plate 120 are brought toward one another.The inner face of the back plate 114 will engage the fabric and tend tourge it under compression generally radially outwardly. The fabric willthen be enclosed generally within the recess 118 of the body portion andwill generally conform to the inner surface of that recess. If oneprevents the entire clamp 15 from passing through the clamp port 124,the fabric will be spaced slightly away from the inner surface of theface 122, yielding a slight dome shape in the forward end 84 of thedevice, as illustrated in FIG. 6. Although the illustrated embodimentincludes such a dome-shaped forward end, it is to be understood that theforward end may be substantially flat (except for the clamp 15), whichcan be accomplished by allowing the clamp to be received entirely withinthe clamp port 124 in the end plate.

[0092] Once the fabric is compressed in the molding element 100 so thatit generally conforms to the molding surface of the molding element, thefabric can be subjected to a heat treatment such as is outlined above.When the molding element is opened again by moving the body portion 110and the end plate 120 away from one another again, the fabric willgenerally retain its deformed, compressed configuration. The device canthen be collapsed, such as by urging the clamps 15, 90 generally axiallyaway from one another, which will tend to collapse the device toward itsaxis. The collapsed device 80 can then be passed through a catheter fordeployment in a channel in a patient's vascular system.

[0093]FIG. 8 schematically illustrates how a medical device 80 generallyas outlined above can be used to occlude a patent ductus arteriosus. Inthis case, there is a shunt, referred to as a PDA above, which extendsbetween a patient's aorta A and the pulmonary artery P. The device 80can be passed through the PDA, such as by keeping the device collapsedwithin a catheter (not shown), and the forward end 84 of the device canbe allowed to elastically expand to substantially recover its thermallyset, “remembered” shape from the heat treatment process, such as byurging the device distally to extend beyond the distal end of thecatheter. This forward end 84 should be larger than the lumen of theshunt of the PDA.

[0094] The device can then be retracted so that the forward end 84engages the wall of the pulmonary artery P. If one continues to retractthe catheter, the engagement of the device with the wall of thepulmonary artery will tend to naturally pull the body portion 82 of thedevice from the catheter, which will permit the body portion to returnto its expanded configuration. The body portion should be sized so thatit will frictionally engage the lumen of the PDA's shunt. The device 80will then be held in place by the combination of the friction betweenthe body portion and the lumen of the shunt and the engagement betweenthe wall of the pulmonary artery and the forward end 84 of the device.Over a relatively short period of time, thrombi will form in and on thedevice 80 and the thrombi will occlude the PDA. If so desired, thedevice may be coated with a suitable thrombolytic agent to speed up theocclusion of the PDA.

[0095]FIGS. 9A and 9B are a side view and an end view, respectively, ofyet another embodiment of the present invention. This device 180 can beused for a variety of applications in a patient's blood vessels. Forexample, if a fabric having a relatively high pick (i.e. where the wiredensity is fairly great) is used in making the device, the device can beused to occlude blood vessels. In other applications, it may serve as afilter within a channel of a patient's body, either in a blood vessel orin another channel, such as in a urinary tract or biliary duct. In orderto further enhance or reduce the device's tendency to occlude thevessel, depending on the application of the device a suitable knownthrombogenic or antithrombogenic coating may be applied to the device.

[0096] This filter 180 has a generally conical configuration, taperinggenerally radially outwardly from its rearward end 182 to its forwardend 184. A length of the device adjacent its forward end is adapted toengage the walls of a lumen of a channel. The maximum diameter of thefilter device 180 is therefore at least as large as the inner diameterof the channel in which it is to be positioned so that at least theforward end will engage the wall of the vessel to substantially lock thedevice in place.

[0097] Having a series of unsecured ends 185 of the wire strandsadjacent the forward end of the device will assist in seating the devicein the channel because the ends of the wires will tend to dig into thevessel wall slightly as the forward end of the device urges itselftoward its fully expanded configuration within the vessel. Thecombination of the friction between the outwardly urging forward end ofthe device and the tendency of the wire ends to dig into the vesselwalls will help ensure that the device remains in place where it isdeployed rather than floating freely within a vessel to reach anundesired location.

[0098] The method in which the device 180 of the invention is deployedmay vary depending on the nature of the physiological condition to betreated. For example, in treating an arterio-venous fistula, the devicemay be carefully positioned, as described above, to occlude the flow ofblood at a fairly specific location. In treating other conditions (e.g.an arterio-venous malformation), however, it may be desired to simplyrelease a number of these devices upstream of the malformation in avessel having a larger lumen and simply allow the devices to drift fromthe treatment site to lodge in smaller vessels downstream.

[0099] The decision as to whether the device 180 should be preciselypositioned at an exact location within the channel in a patient's bodyor whether it is more desirable to allow the device(s) to float to theirfinal lodging site will depend on the size of the channels involved andthe specific condition to be treated. This decision should be left tothe individual operator to be made on a case-by-case basis as his or herexperience dictates; there is no one right or wrong way to deploy thedevice 180 without regard to the conditions at hand.

[0100] In the embodiment shown in FIGS. 9A and 9B, the wall of thedevice extends generally linearly from a position adjacent the clamp 90and the other end of the device, approximating a conical shape. Due tothe presence of the clamp 90, though, the end of the device immediatelyadjacent the clamp may deviate slightly from the cone shape, asindicated in the drawings. Alternatively, the wall may be curved so thatthe diameter of the device changes more rapidly adjacent the rearwardend than it does adjacent its forward end, having an appearance morelike a rotation of a parabola about its major axis than a true cone.Either of these embodiments should suffice in occluding a vessel withthe device 180, such as to occlude a vessel.

[0101] The ends of the wire strands at the rearward end 182 of thedevice are secured with respect to one another, such as by means of athreaded clamp 90 such as that described above in connection with FIGS.6A-6C. Portions of the wire strands adjacent the forward end 184 mayalso be secured against relative movement, such as by spot welding wiresto one another where they cross adjacent the forward end. Such a spotweld is schematically illustrated at 186 in FIGS. 9A and 9B.

[0102] In the embodiment illustrated in FIG. 9, though, the ends of thewire strands adjacent the forward end 184 in the finished device neednot be affixed to one another in any fashion. These strands are held ina fixed position during the forming process to prevent the metal fabricfrom unraveling before it is made into a finished device. While the endsof the wire strands adjacent the forward end remain fixed relative toone another, they can be heat treated, as outlined above. The heattreatment will tend to fix the shapes of the wires in their deformedconfiguration wherein the device generally conforms to a molding surfaceof the molding element. When the device is removed from contact with themolding element, the wires will retain their shape and tend to remainintertwined. Accordingly, when the device is released from contact withthe molding element, even if the ends of the wires are released from anyconstraint the device should stiff substantially retain its shape.

[0103] FIGS. 10A-10C illustrate three suitable molds for use in formingthe filter 180 of FIGS. 9A and 9B. In FIG. 10A, the molding element 200is a single piece which defines a pair of generally conical portionsabutting one another. In another similar embodiment (not shown), themolding element 200 may be generally ovoid, shaped not unlike anAmerican football or a rugby ball. In the embodiment illustrated in FIG.10A, though, the molding element is a little bit less rounded. Thismolding element comprises two conical segments 202 which abut oneanother at their bases, defining a larger diameter at the middle 204 ofthe element which can taper relatively uniformly toward the ends 206 ofthe element 200.

[0104] When a tubular braid is used in forming this device, the tubularmetal fabric may be applied to the molding element by placing themolding element within the tubular braid and clamping the ends of thebraid about the molding element before cutting the braid to the desiredlength. In order to better facilitate the attachment of the clamps 90 tothe ends of the tubular braid, the ends 206 of the molding element maybe rounded, as shown, rather than tapering to a sharper point at theends of the molding element. In order to ensure that the braid moreclosely conforms to the outer surface of the molding element 200, i.e.the molding element s molding surface, the natural, relaxed diameter ofthe braid should be less than the maximum diameter of the element, whichoccurs at its middle 204. This will place the metal fabric in tensionabout the middle of the element and, in combination with the clamps atthe ends of the braid, cause the braid to generally conform to themolding surface.

[0105]FIG. 10B illustrates an alternative molding element 210 forforming a device substantially as shown in FIGS. 9A and 9B. Whereas themolding element 200 is intended to be received within a recess in themetal fabric, such as within the lumen of a length of tubular braid, themolding element 210 has an internal cavity 212 adapted to receive thefabric. In this embodiment, the molding element may comprise a pair ofmolding sections 214, 216 and these mold sections may be substantiallyidentical in shape. Each of the molding sections 214, 216 generallycomprise a conical inner surface 220 defined by a wall 222. Each sectionalso may be provided with a generally cylindrical axial recess 224 forreceiving a clamp 15 (or 90) carried by an end of the metal fabric.

[0106] The two molding sections should be readily attached to oneanother with the larger, open ends 226 of the sections abutting oneanother. The mold sections can simply be clamped together, such as byproviding a reusable jig (not shown) which can be used to properlyposition the sections 214, 216 with respect to one another. If sodesired, bolt holes 228 or the like may be provided to allow a nut andbolt, or any similar attachment system, to be passed through the holesand attach the sections 214, 216 together.

[0107] In use, a suitably sized piece of a metal fabric, optimally alength of a tubular braid, is placed in the recess 212 of the moldingelement and the two molding sections 214, 216 are urged toward oneanother. The fabric should have a relaxed axial length longer than theaxial length of the recess 212 so that bringing the sections toward oneanother will axially compress the fabric. This axial compression willtend to urge the wire strands of the braid radially outwardly away fromthe axis of the braid and toward engagement with the molding surface ofthe element 210, which is defined by the surface of the recess 212.

[0108] Once the metal fabric is deformed to generally conform to themolding surface of either molding element 200 or 210, the fabric can beheat treated to substantially set the shape of the fabric in itsdeformed state. If molding element 200 is used, it can then be removedfrom the interior of the metal fabric. If there is sufficient roombetween the resilient wire strands, the molding element can simply beremoved by opening the web of wire strands and pulling the moldingelement out of the interior of the metal fabric. If molding element 210is employed, the two molding sections 214, 216 can be moved away fromone another and the molded fabric can be retrieved from the recess 212.Depending on the shape of the molding surface, the resulting formedshape may resemble either a pair of abutting hollow cones or, as notedabove, a football, with clamps, welds or the like provided at either endof the shape.

[0109] This shape can then be cut into two halves by cutting the wiresin a direction generally perpendicular to the shared axis of the cones(or the major axis of the ovoid shape) at a location about midway alongits length. This will produce two separate filter devices 180substantially as illustrated in FIGS. 9A and 9B. If the wire strands areto be joined adjacent the forward end of the device (such as by theweldments shown as 186 in FIGS. 9A and 9B), this can be done before theconical or ovoid shape is severed into two halves. Much the same netshape could be accomplished by cutting the metal fabric into halveswhile it is still carried about molding element 200. The separate halveshaving the desired shape could then be pulled apart from one another,leaving the molding element ready for forming additional devices.

[0110] In an alternative embodiment of this method, the molding element200 is formed of a material selected to permit the molding element to bedestroyed for removal from the interior of the metal fabric. Forexample, the molding element may be formed of a brittle or friablematerial, such as glass. Once the material has been heat treated incontact with the molding surface of the molding element, the moldingelement can be broken into smaller pieces which can be readily removedfrom within the metal fabric. If this material is glass, for example,the molding element and the metal fabric can be struck against a hardsurface, causing the glass to shatter. The glass shards can then beremoved from the enclosure of the metal fabric. The resultant shape canbe used in its generally conical shape, or it can be cut into twoseparate halves to produce a device substantially as shown in FIGS. 9Aand 9B.

[0111] Alternatively, the molding element 200 can be formed of amaterial which can be chemically dissolved, or otherwise broken down, bya chemical agent which will not substantially adversely affect theproperties of the metal wire strands. For example, the molding elementcan be formed of a temperature-resistant plastic resin which is capableof being dissolved with a suitable organic solvent. The fabric and themolding element can be subjected to a heat treatment to substantiallyset the shape of the fabric in conformance with the surface of themolding element, whereupon the molding element and the metal fabric canbe immersed in the solvent. Once the molding element is substantiallydissolved, the metal fabric can be removed and either used in itscurrent shape or cut into separate halves, as outlined above.

[0112] Care should be taken to ensure that the material selected to formthe molding element is capable of withstanding the heat treatmentwithout losing its shape, at least until the shape of the fabric hasbeen set. For example, the molding element could be formed of a materialhaving a melting point above the temperature necessary to set the shapeof the wire strands, but below the melting point of the metal formingthe strands. The molding element and metal fabric can then be heattreated to set the shape of the metal fabric, whereupon the temperaturecan be increased to substantially completely melt the molding element,thereby removing the molding element from within the metal fabric.

[0113] It should be understood that the methods outlined immediatelyabove for removing the metal fabric 10 from the molding element 200 canbe used in connection with other shapes, as well. Although these methodsmay not be necessary or desirable if the molding element is carriedabout the exterior of the metal fabric (such as are elements 30-40 ofthe molding element 20 of FIGS. 2-4), if the molding element or someportion thereof is enclosed within the formed metal fabric (such as theinternal molding section of the molding element 20), these methods canbe used to effectively remove the molding element without adverselyaffecting the medical device being formed.

[0114]FIG. 10C illustrates yet another molding element 230 which can beused in forming a medical device such as that illustrated in FIGS. 9Aand 9B. This molding element comprises an outer molding section 232defining a tapered inner surface 234 and an inner molding section 236having an outer surface 238 substantially the same shape as the taperedinner surface 234 of the outer molding section. The inner moldingsection 236 should be sized to be received within the outer moldingsection, with a piece of the metal fabric (not shown) being disposedbetween the inner and outer molding sections. The molding surface ofthis molding element 230, to which the fabric will generally conform,can be considered to include both the inner surface 234 of the outermolding section and the outer surface 238 of the inner molding section.

[0115] This molding element 230 can be used with a metal fabric which isin the form of a tubular braid. If such a fabric is used and a clamp 15(not shown in this drawing) or the like is provided to connect the endsof the wire strands adjacent one end of the device, a recess (not shown)analogous to the cavity 46 in the face of the compression disk 44 ofmolding element 20 (FIGS. 2-4) can be provided for receiving the clamp.

[0116] However, the present molding element 230 can be used quitereadily with a Flat woven piece of metal fabric, such as is illustratedin FIG. 1B. In using such a fabric, a suitably sized and shaped piece offabric is cut; in using the molding element 230 to produce a device 180analogous to that shown in FIGS. 9A and 9B, for example, a generallydisk-shaped piece of the metal fabric 10′ can be used. The metal fabricis then placed between the two sections 232, 236 of the molding elementand the sections are moved together to deform the fabric therebetween.After heat treatment, the fabric an be removed and will retainsubstantially the same shape as it had when it was deformed between thetwo molding sections.

[0117] As can be seen by the discussion of the various molding elements200, 210 and 230 in FIGS. 10A-10C, it should be clear that a number ofdifferent molding elements may achieve essentially the same desiredshape. These molding elements may be received entirely within a closedsegment of fabric and rely on tension and/or compression of the fabricto cause it to generally conform to the molding surface of the moldingelement, as with the element 200 of FIG. 10A. The molding element 210 ofFIG. 10B substantially encloses the fabric within a recess in the moldand relies on compression of the fabric (in this case axial compressionof a tubular braid) to deform the fabric to the desired configuration.Finally, the fabric may be compressed between two coacting parts of themolding element to deform the fabric, such as between the two sections232, 236 of molding element 230 in FIG. 10C. Any one or more of thesetechniques may be used in achieving a finished product having a desiredshape.

[0118]FIGS. 11 and 12 illustrate alternative embodiments of yet anothermedical device in accordance with this invention. Both FIG. 11 and FIG.12 illustrate a vascular trap suitable for use in temporarily filteringembolic particles from blood passing through a patient's vascularsystem. Such a device will most frequently be used to filter emboli froma patient's blood when another medical procedure is being performed,such as by using the trap in conjunction with a rotating cutting bladeduring an atherectomy or with a balloon catheter during angioplasty. Itis to be understood, though, that the trap could also be used in othersimilar applications, such as in channels in patients' bodies other thantheir vascular systems.

[0119] In the embodiment of FIGS. 11A and 11B, the vascular trap 250comprises a generally umbrella-shaped basket 270 carried adjacent adistal end of a guidewire 260. The guidewire in this embodiment includesa tapered distal section 262 with a spirally wound coil 264 extendingalong a distal length of the wire. Guidewires having such a distal endare conventional in the art. The basket 270 is positioned generallydistally of the coil 264, and is desirably attached to the guidewireproximally of the proximal end of the tapered section, as shown.

[0120] The basket 270 (Shown in its collapsed configuration in FIG. 11A)includes a distal band 272 and a proximal band 274. The distal band maybe made of a radiopaque material, such as gold, platinum or tungsten,and is affixed directly to the shaft of the guidewire 260. Thisattachment may be made by any suitable means, such as by welding,brazing, or soldering. Alternatively, the distal band 272 may comprise abead of a biocompatible cementitious material, such as a curable organicresin. If it is desired to increase the visibility of the band forfluoroscopic observation, a radiopaque metal or the like can be imbeddedin the cementitious material. The proximal band 274 may be formed of ahypotube sized to permit the tube to slide along the guidewire duringdeployment. This hypotube may be made of a metallic material; athin-walled tube of a NiTi alloy should suffice. If so desired, theproximal band may be formed of a more radiopaque metal, or a NiTi alloyband can have a radiopaque coating applied to its surface.

[0121] The body of the device is formed of a metal fabric, as explainedabove. The metal fabric of this embodiment is optimally initially formedas a tubular braid and the ends of the wires forming the braid can beattached together by means of the bands 272, 274 before the fabric iscut to length. Much like the clamps 15, 90 noted above, these bands 272,274 will help prevent the metal fabric from unraveling during theforming process. (The method of forming the basket 270 is describedbelow in connection with FIG. 16.)

[0122] When the device is in its collapsed state for deployment in apatient's vessel (as illustrated in FIG. 11A), the basket 270 will becollapsed toward the axis of the guidewire 260. The distal 272 andproximal 274 bands are spaced away from one another along the length ofthe guidewire, with the fabric of the device extending therebetween. Ina preferred embodiment, when the basket is in its collapsed state itwill engage the outer surface of the guidewire to permit the device tobe deployed through a relatively small lumen of a catheter or anothermedical device.

[0123] When the device is deployed in a patient's vascular system, thebasket will take on an expanded configuration wherein it extendsoutwardly of the outer surface of the guidewire. As best seen in FIG.11B, the shape of the basket 270 when deployed may generally resemble aconventional umbrella or parachute, having a dome-like structure curvingradially outwardly from the guidewire moving proximally from the distalband 272. It is to be understood that other suitable shapes could easilyperform the desired filtering function, such as a conical shape whereinthe slope of the device changes more linearly than the smooth, roundedversion shown in FIG. 11B. It is also believed that a relatively flat,disc shape would also suffice. In this expanded configuration, the twobands 272, 274 are closer together, with the distal band 272 optimallybeing spaced only a short distance from the proximal band 274, asillustrated.

[0124] In moving from its collapsed state (FIG. 11A) to its expandedstate (FIG. 11B), the metal fabric turns in on itself, with a proximalportion 282 of the collapsed basket being received within the interiorof a distal portion 284 of the collapsed basket. This produces atwo-layered structure having a proximal lip 286 spaced radiallyoutwardly of the guidewire, defining a proximally-facing cup-shapedcavity 288 of the basket. When blood (or any other fluid) flows throughthe basket in a distal direction, any particulate matter in the blood,e.g. emboli released into the bloodstream during atherectomy orangioplasty procedures, will tend to be trapped in the cavity 288 of thebasket.

[0125] The precise dimensions of the metal fabric can be varied asdesired for various applications. If the device 250 is to be used as avascular filter to trap emboli released into the blood, for example, thepores (i.e. the openings between the crossing metal strands) of thefabric are desirably on the order of about 1.0 mm. This is generallydeemed to be the minimum size of any particles which are likely to causeany adverse side effects if they are allowed to float freely within ablood vessel. One would not want to make the pores too small, though,because the blood (or other fluid) should be free to pass through thewall of the basket 270. If so desired, the basket may be coated with asuitable anti-thrombogenic coating to prevent the basket from occludinga blood vessel in which it is deployed.

[0126] When a fabric having 1.0 mm pores is used to form the basket 270of this embodiment of the invention, the forming process will reorientthe wires relative to one another and in some areas (e.g. adjacent theproximal lip 286) the pores will be larger than 1.0 mm. However, becausethe basket's walls are formed of essentially two thicknesses 282, 284 ofthe fabric, the effective pore size of the device may be significantlyreduced even at these locations.

[0127] The device 250 may also be provided with tethers 290 forcollapsing the basket 270 during retraction. The basket may include fourindependent tether wires, each of which extends proximally from theproximal lip 286 of the deployed basket. In a preferred embodiment,though, the four tether wires illustrated in the drawings are actuallyformed of two longer wires, with each wire extending peripherally abouta portion of the proximal lip of the basket. These tether wires may beintertwined with the wires of the metal fabric to keep the tethers inplace during use. When the tethers are retracted or drawn down towardthe guidewire, the wires extending along the proximal lip of the basketwill tend to act as drawstrings, drawing the proximal end of the basketradially inwardly toward the guidewire. This will tend to close thebasket and entrap any material caught in the cavity 288 of the basketduring use so that the basket can be retracted, as detailed below.

[0128] The tether wires 290 may extend along much of the length of theguidewire so that they will extend outside the patient's body during useof the device 250. When it is desired to collapse the basket forretrieval, the operator can simply hold the guidewire 260 steady andretract the tethers with respect to the guidewire. This can tend to berelatively cumbersome, though, and may be too difficult to effectivelyaccomplish without breaking the tethers if the device is deployed at aselective site reached by a tortuous path, such as in the brain.

[0129] Accordingly, in the preferred embodiment shown in FIGS. 11A and11B, the tethers 290 are attached to the guidewire 260 at a positionspaced proximally of the basket. The tethers may, for example, beattached to a metal strap 292 or the like and this strap 292 may beaffixed to the shaft of the guidewire. When it is desired to close theproximal end of the basket for retraction, an external catheter (notshown) can be urged distally toward the basket 270. When the catheterencounters the radially extending tethers, the distal end of thecatheter will tend to draw the tethers toward the guidewire as thecatheter is advanced, which will, in turn, tend to draw the proximal endof the basket closed.

[0130]FIGS. 12A and 12B illustrate an alternative embodiment of thedevice shown in FIGS. 11A and 11B, with FIG. 12A showing the devicecollapsed in a catheter C for deployment and FIG. 12B showing the devicein its deployed configuration. In the embodiment shown in FIGS. 12A and12B, the basket 270 is formed substantially the same as outlined abovein connection with FIGS. 11A and 11B. In the embodiment of FIGS. 12,though, the distal band 272 is affixed to the guidewire 260′ at thedistal tip of the guidewire. The guidewire 260′ is of the type referredto in the art as a “movable core” guidewire. In such guidewires, a corewire 265 is received within the lumen of a helically wound wire coil 266and the core wire 265 extends distally beyond the distal end of the coil266. A thin, elongate safety wire 268 may extend along the entire lumenof the coil 266 and the distal end of the safety wire may be attached tothe distal end of the coil to prevent loss of a segment of the coil ifthe coil should break.

[0131] In the embodiment of FIG. 11, the proximal ends of the tethers290 are attached to a metal strap 292 which is itself attached to theshaft of the guidewire 260. In the present embodiment, the tethers arenot attached to the core wire 265 itself. Instead, the tethers areattached to the coil 266 of the guidewire. The tethers may be attachedto the coil by any suitable means, such as by means of laser spotwelding, soldering or brazing. The tethers 290 may be attached to thecoil 266 at virtually any spot along the length of the coil. Asillustrated in these drawings, for example, the tethers may be attachedto the coil adjacent the coil's distal end. However, if so desired thetethers may be attached to the coil at a location space more proximallyfrom the basket 270.

[0132] An external catheter such as that referred to in the discussionof FIG. 11A, but not shown in those drawings, is illustrated in FIGS.12A and 12B. Once the basket 270 is deployed in a patient's vessel tosubstantially reach the expanded configuration shown in FIG. 12B and thebasket has performed its intended filtration function, the externalcatheter C can be urged distally toward the basket 270. As this catheteris urged forward, the tethers will tend to be drawn into the distal endof the catheter, which is substantially narrower than the proximal lip286 of the basket. This will tend to draw the tethers down toward theguidewire and help close the basket, as explained above.

[0133] FIGS. 13-15 illustrate yet another alternative embodiment of avascular trap in accordance with the present invention. This vasculartrap 300 includes a basket 320 received over a guidewire 310. In mostrespects, the basket 320 is directly analogous to the basket 270illustrated in FIGS. 11-12. The basket 320 includes a proximal band 322and a distal band 324. As in the embodiment of FIGS. 12A and 12B, thedistal band may be attached to the guidewire adjacent its distal end. Ifso desired, though, a structure such as is shown in FIG. 11, wherein theguidewire extends distally beyond the basket, could instead be used.

[0134] As best seen in its collapsed state (shown in FIG. 12A), thebasket includes a distal segment 325 and a proximal segment 326, withthe distal end of the distal segment being attached to the distal band324 and the proximal end of the proximal segment being attached to theproximal band 322. When the basket 320 is in the expanded configuration(shown in FIG. 12B), the proximal segment 326 is received within thedistal segment 325, defining a proximal lip 328 at the proximal edge ofthe device. The wall of the basket thus formed also includes a cavity329 for trapping solids entrained in a fluid, such as emboli in apatient's blood stream.

[0135] The basket 320 of FIGS. 13-15 is also shaped a little bitdifferently than the basket 270 of the previous drawings. The primarydifference between these two baskets is that the basket 320 is a littlebit shorter along its axis than is the basket 270. This different basketshape is simply intended to illustrate that the basket of a vasculartrap in accordance with the invention can have any of a wide variety ofshapes and no particular significance should be attached to the slightlydifferent shapes shown in the various drawings.

[0136] In the vascular traps 250 and 250′ of FIGS. 11 and 12,respectively, tethers were used to draw down the proximal end of thebasket 270 to close the basket for retraction. In the embodiment shownin FIGS. 13-15, though, the trap 300 includes a basket cover 340positioned proximally of the basket 320. The basket cover may also beformed of a metallic tubular braid and is also adapted to be collapsedto lay generally along the outer surface of the guidewire 310. The cover340 is not directly affixed to the guidewire at any point, though, butis instead intended to be slidable along the guidewire. As best seen inFIGS. 13 and 14 wherein the cover is in its collapsed state, the cover340 includes a distal hypotube 342 and a proximal control hypotube 344,with the distal hypotube being attached to the distal end of the cover340 and the proximal control hypotube 344 being attached to the proximalend of the cover.

[0137] The cover 340 is shown in its deployed, expanded configuration inFIG. 15. As shown in that figure, the cover has a similar structure tothat of the basket 320, but is oriented to be open distally rather thanproximally, as is the basket. As best seen in FIGS. 13 and 14 whereinthe cover is in its collapsed state, the cover has a distal segment 352and a proximal segment 354. When the cover is deployed by urging itdistally out of the distal end of the deployment catheter C, the cover340 will tend to resiliently return to its expanded configuration andthe distal hypotube 342 will slide axially proximally along theguidewire toward the proximal control hypotube 344. This will invert thecollapsed cover so that the distal section 352 is generally receivedwithin the proximal section 354, defining a distal lip 358 of the cover.

[0138] The proximal control hypotube 344 may extend along a substantialportion of the length of the catheter 310 so that it extends out of thepatient's body when the device 300 is in place. By grasping the controlhypotube and moving it relative to the guidewire 310, an operator cancontrol the position of the cover 340 with respect to the basket 320,which is affixed to the guidewires. As explained in more detail below inconnection with the use of the device 300, once the basket has beendeployed and has been used to filter objects entrained in the fluid(e.g. emboli in blood), the cover 340 may be deployed and the trap maybe drawn proximally toward the cover by moving the guidewire proximallywith respect to the control hypotube 344.

[0139] The inner diameter of the distal lip 358 of the cover isdesirably slightly larger than the outer diameter of the proximal lip328 of the basket. Hence, when the basket is drawn proximally toward thecover it will be substantially enclosed therein. The cover willtherefore tend to trap any emboli (not shown) or other particulatematter retained within the cavity 330 of the basket. A retrieval sheathS may then be urged distally to engage the outer surface of the cover340. This will tend to cause the cover to collapse about the basket,tightly engaging the outer surface of the basket. This somewhatcollapsed structure can then be withdrawn from the patient's channel andremoved from the patient's body. By enclosing the basket within thecover, the likelihood of any filtered debris within the basket beinglost as the basket is retrieved will be substantially eliminated.

[0140] The guidewire and the metal fabric can be of any diametersuitable for the intended application of the vascular trap 250, 250′ or300. In a preferred embodiment, the guidewire is between about 0.014″and about 0.038″ in diameter and the wires of the metal fabric used toform the basket (and the cover 340, if a cover is included) are betweenabout 0.002″ and about 0.006″. The thickness of the metal bands (272,274 or 322, 324) also is desirably in the range of about 0.002″-0.006″.

[0141] In one particularly preferred embodiment intended to be used innarrower vessels such as those encountered in cerebral and coronaryapplications, the guidewire has an outer diameter of about 0.014″ andthe wires of the metal fabric are about 0.002″ in diameter. The metalbands in this embodiment may also have a thickness of about 0.002″ sothat they will not be substantially wider than the collapsed basket.When the device is collapsed for deployment through a catheter, it willhave an outer diameter of about 0.018″, permitting the device to be usedwith catheters and other instruments adapted for use with a 0.018″guidewire.

[0142]FIG. 16 illustrates one embodiment of a molding element 370 whichmay be used in making a basket 270. Although the basket 320 and cover340 of the trap 300 are shaped somewhat differently, an analogousmolding element can be used for these portions of the trap 300 as wellby simply modifying some of the dimensions of the molding element 370,but retaining the basic shape and structure of the molding element. Italso should be understood that the molding element 370 is merely onepossible molding element for forming a shape such as that of the basket270 and that any one of a variety of different molding elements will beapparent to those skilled in the art, as noted above in connection withFIGS. 10A-C.

[0143] The molding element 370 has an outer molding section 372 defininga curved inner surface 374 and an inner molding section 376 having anouter surface 378 substantially the same shape as the curved innersurface 374 of the outer molding section. The inner molding section 376should be sized to be received within the outer molding section, with apiece of the metal fabric (not shown) being disposed between the innerand outer molding sections. In a preferred embodiment, the inner surface374 of the outer molding element and the outer surface 378 of the innermolding section each include a recess (375 and 379, respectively) forreceiving an end of the braid. The molding surface of this moldingelement 370, to which the fabric will generally conform, can beconsidered to include both the inner surface 374 of the outer moldingsection and the outer surface 378 of the inner molding section.

[0144] In use, the two molding sections 372, 376 are spaced apart fromone another and a length of a tubular braid of metal fabric (not shownin FIG. 16) is disposed between these molding sections. Optimally, oneend of the fabric is placed in the recess 375 of the outer moldingsection and the other end of the fabric is placed in the recess 379 inthe inner molding section. The inner and outer molding sections can thenbe urged generally toward one another. As the ends of the wire approachone another, the tubular braid will tend to invert upon itself and asurface of the tubular braid will generally conform to either the innersurface 374 of the outer molding section or the outer surface 378 of theinner molding section, arriving at a shape analogous to that of thebasket 270 of the traps 250, 250′. The two molding sections can then belocked in place with respect to one another and the metal fabric may beheat treated to set the wires in this deformed configuration.

[0145] The method in accordance with the present invention furtherincludes a method of treating a physiological condition of a patient. Inaccordance with this method, a medical device suitable for treating thecondition, which may be substantially in accordance with one of theembodiments outlined above, is selected. For example, if a patent ductusarteriosus is to be treated, the PDA occlusion device 80 of FIGS. 6A-6Ccan be selected. Once the appropriate medical device is selected, acatheter may be positioned within a channel in a patient's body to placethe distal end of the catheter adjacent the desired treatment site, suchas immediately adjacent (or even within) the shunt of the PDA.

[0146] Medical devices made in accordance with the method of theinvention outlined above have a preset expanded configuration and acollapsed configuration which allows the device to be passed through acatheter. The expanded configuration is generally defined by the shapeof the medical fabric when it is deformed to generally conform to themolding surface of the molding element. Heat treating the metal fabricsubstantially sets the shapes of the wire strands in the reorientedrelative positions when the fabric conforms to the molding surface. Whenthe metal fabric is then removed from the molding element, the fabricmay define a medical device in its preset expanded configuration.

[0147] The medical device can be collapsed into its collapsedconfiguration and inserted into the lumen of the catheter. The collapsedconfiguration of the device may be of any shape suitable for easypassage through the lumen of a catheter and proper deployment out thedistal end of the catheter. For example, the devices shown in FIG. 5 mayhave a relatively elongated collapsed configuration wherein the devicesare stretched along their axes. This collapsed configuration can beachieved simply by stretching the device generally along its axis, e.g.by manually grasping the clamps 15 and pulling them apart, which willtend to collapse the expanded diameter portions 64 of the device 60inwardly toward the device's axis. The PDA occlusion device 80 of FIGS.6 also operates in much the same fashion and can be collapsed into itscollapsed configuration for insertion into the catheter by applyingtension generally along the axis of the device. In this regard, thesedevices 60 and 80 are not unlike “Chinese handcuffs”, which tend toconstrict in diameter under axial tension.

[0148] Once the medical device is collapsed and inserted into thecatheter, it may be urged along the lumen of the catheter toward thedistal end of the catheter. This may be accomplished by using aguidewire or the like to abut against the device and urge it along thecatheter. When the device begins to exit the distal end of the catheter,which is positioned adjacent the desired treatment site, it will tend toresiliently return substantially entirely to its preset expandedconfiguration. Superelastic alloys, such as nitinol, are particularlyuseful in this application because of their ability to readily return toa particular configuration after being elastically deformed to a greatextent. Hence, simply urging the medical device out of the distal end ofthe catheter tend to properly deploy the device at the treatment site.

[0149] Although the device will tend to resiliently return to itsinitial expanded configuration (i.e. its shape prior to being collapsedfor passage through the catheter), it should be understood that it maynot always return entirely to that shape. For example, the device 60 ofFIG. 5 is intended to have a maximum outer diameter in its expandedconfiguration at least as large as and preferably larger than, the innerdiameter of the lumen in which it is to be deployed. If such a device isdeployed in a vessel having a small lumen, the lumen will prevent thedevice from completely returning to its expanded configuration.Nonetheless, the device would be properly deployed because it wouldengage the inner wall of the lumen to seat the device therein, asdetailed above.

[0150] If the device is to be used to permanently occlude a channel inthe patient's body, such as the devices 60 and 80 described above maybe, one can simply retract the catheter and remove it from the patient'sbody. This will leave the medical device deployed in the patient'svascular system so that it may occlude the blood vessel or other channelin the patient's body. In some circumstances, the medical device may beattached to a delivery system in such a manner as to secure the deviceto the end of the delivery means, such as when the threaded clamp 90shown in FIGS. 6 and 9 are attached to a distal end of the deliverymeans, as explained above. Before removing the catheter in such asystem, it may be necessary to detach the medical device from thedelivery means before removing the catheter and the delivery means.

[0151] The devices of FIGS. 11-15 may be deployed in much the samefashion outlined above. However, these devices 250, 250′ and 300 areadvantageously deployed for use in conjunction with another medicaldevice and will most frequently be retracted from the patient's bodyafter use.

[0152] For example, any one of these devices are suitable for use inconjunction with a balloon angioplasty procedure. In such procedures,catheters having inflatable balloons at their ends, referred to asballoon catheters, are positioned within a blood vessel so that theballoon is positioned within a stenosis. These balloons are positionedby tracking the balloon catheter along a guidewire or the like; theballoons typically have a central bore therethrough. Once the balloon isproperly positioned, it is inflated and urges radially outwardly againstthe stenosis. This will tend to squeeze the stenosis against the wallsof the vessel, improving patency of the vessel.

[0153] When the stenosis is treated in this fashion, though, there is arisk that some debris will break free and enter the blood flowingthrough the vessel. If left unchecked, this embolus can drift downstreamand embolize a distal portion of the vessel. Depending on where theembolus comes to rest, the embolization can result in significant tissueor organ damage. This risk is particularly acute in cardiac and coronaryapplications because the embolization can result in a myocardialinfarction or heart attack, and in neurovascular and interventionalradiological procedures the embolization can lead to a stroke or damageto brain tissue.

[0154] In order to prevent, or at least substantially limit, suchembolization, a vascular trap 250, 250′ or 300 of the invention can beused with the balloon catheter. The device should be sized to permit itto be passed through the lumen of the particular balloon catheter to beused in the angioplasty.

[0155] In one embodiment of a method for using such a vascular trap, thetrap is deployed first. The basket (270 or 320) of the trap will beguided to a position located downstream of the desired treatment sitethrough an introduction catheter (e.g. the catheter C in FIGS. 12-15).The basket is then urged distally beyond the end of the catheter, whichwill permit the basket to resiliently substantially return to itsexpanded configuration from its collapsed configuration within thecatheter. Once the trap is in place, the balloon catheter can beexchanged for the introduction catheter, and the balloon catheter cantrack the guidewire (260 or 310) of the vascular trap. The balloon canthen be positioned within the stenosis and expanded, as outlined above.Once the angioplasty has been completed, the balloon can be deflatedagain and withdrawn proximally out of the patient.

[0156] In an alternative embodiment of the present method, the ballooncatheter can be used to perform the same function as performed by theintroduction catheter in the preceding embodiment. In this embodiment,the balloon catheter is positioned in the patient's vessel so that thedistal end of the balloon catheter is located downstream of thestenosis. The vascular trap (250, 250′ or 300) of the invention is thenpassed through the lumen of the balloon catheter and the basket is urgedout of the distal end of the catheter. The basket will resilientlysubstantially return to its preferred expanded configuration, whereuponthe balloon catheter can be retracted along the shaft of the device'sguidewire until the balloon is properly positioned within the stenosis.

[0157] If so desired, the balloon catheter can instead be provided witha length of standard catheter extending distally beyond the distal endof the balloon. The balloon can then be positioned within the stenosisand the basket can be urged out of the distal end of the distalextension of the catheter. In such an embodiment, the length of thedistal extension of the catheter should be sufficient to properlyposition the basket with respect to the balloon when the basket exitsthe distal end of the catheter. This will eliminate the need to performthe separate step of retracting the balloon into position within thestenosis after the basket is deployed. The balloon can then be expanded,deflated and withdrawn as described above.

[0158] Much the same procedure can be used to deploy a vascular trap ofthe invention for use in an atherectomy procedure. In such procedures, acutting head is positioned at the distal end of an elongate, hollowshaft and the cutting head has a bore extending therethrough. The trapcan be deployed in either of the methods outlined above, but it isanticipated that in most instances the first procedure will be used,i.e. the basket will be deployed with an introduction catheter, whichwill be removed so that the cutting device can be guided over theguidewire of the vascular trap. It should also be understood that thedevice 250, 250′ and 300 could also be used in other medical proceduresin other bodily channels besides a patient's vascular system.

[0159] Since the trap is positioned downstream of the stenosis, anydebris released during the procedure will tend to drift distally towardthe basket and be caught therein. In order to prevent any emboli fromsimply floating past the trap, it is preferred that the proximal lip(288 or 328) of the basket be at least as large as the lumen of thevessel. In a preferred embodiment, the natural dimension of the proximallip (i.e. where the basket has fully returned to its expandedconfiguration) is somewhat greater than the vessel's inner diameter sothat the basket will firmly engage the wall of the vessel.

[0160] The method of retracting the basket will depend on whichembodiment of the vascular trap is used, namely whether or not thedevice includes a cover 340. The device 250 or 250′ of FIG. 11 or 12,respectively, do not include such a cover. However, they do includetethers 290 which extend proximally from the proximal lip 288 of thebasket to an attachment to the guidewire. In either of theseembodiments, a retrieval catheter can be introduced over the guidewireand urged distally toward the basket. As explained above in connectionwith FIGS. 11 and 12, this will tend to draw the tethers down toward theguidewire, effectively closing the proximal end of the basket 270. Oncethe basket is sufficiently closed, such as when the proximal lip of thebasket engages the distal tip of the retrieval catheter, the catheterand the vascular trap can be retracted together from the patient's body.By substantially closing the proximal end of the basket in such afashion, any emboli which are captured in the basket when it is deployedcan be retained within the basket until it is removed from the patient'sbody.

[0161] If so desired, a balloon catheter or like device can instead beused, with the balloon catheter being used to draw down the tethers 290and collapse the basket. The vascular trap can then be withdrawn withthe balloon catheter rather than having to separately introduce aremoval catheter to remove the trap.

[0162] In withdrawing the embodiment illustrated in FIGS. 13-15, thecover 340 is positioned over the proximal lip of the basket before thevascular trap 300 is retracted.

[0163] Once the medical procedure is completed and any debris has beencaptured in the basket, the cover 340 is allowed to resilientlysubstantially return to its expanded configuration. Once it is deployedproximally of the basket, the basket 320 can be drawn proximally towardthe cover 340 until it engages or is received within the cover, as notedabove in connection with FIG. 15.

[0164] In actuality, the cover 340 may be unable to return to its fullexpanded configuration due to the confines of the vessel in which it isdeployed. As explained previously, the cover 340 is desirably largerthan the basket 320 so that the basket can be received within the cover.However, the basket is optimally sized to engage the walls of the vesselto prevent the unwanted passage of emboli or other debris around theedges of the basket. Accordingly, the distal lip 358 of the cover willengage the wall of the channel before it expands to its full size. Thewalls of most bodily channels, such as blood vessels, tend to besomewhat elastic, though. The cover 340 will therefore tend to urgeharder against the wall of the vessel than the smaller basket and maystretch the vessel a little bit more than will the basket. In thisfashion, the cover may still be able to expand to a dimension largeenough to permit the basket to be received in the cavity 356 of thecover. If not, the distal lip 358 of the cover can simply be broughtinto close engagement with the proximal lip 328 of the basket togenerally seal the basket.

[0165] Once the cover 340 is brought into engagement with the basket320, whether by receiving the basket within the cover or, lesspreferably, by engaging the lips 358, 328 of the cover and the basket,the device can be withdrawn proximally from the patient's vascularsystem. The cover will tend to prevent any emboli caught in the basketduring deployment from being inadvertently lost during withdrawal.

[0166] The vascular traps 250, 250′ and 300 of the present inventiontherefore have distinct advantages over other vascular traps or filterscurrently known in the art. As explained above, most prior art traps aredifficult and expensive to form and cannot be readily collapsed forretrieval. The present invention, though, provides a method for makingthe vascular traps 250, 250′ and 300 which is both relativelyinexpensive and less labor intensive, generally resulting in a moreconsistent product than prior art hand-forming methods. Furthermore, thestructure of the device and the methods outlined above for removing thedevice will fairly reliably prevent the inadvertent dumping of trappedemboli back into the bloodstream while the device is being removed.Since most prior art traps and filters are much more difficult to useand are more likely to dump filtered debris back into the bloodstream,the present invention can be substantially safer than these prior artsystems.

[0167] While a preferred embodiment of the present invention has beendescribed, it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. A method of protecting a patient fromembolization during a percutaneous procedure on a vessel, comprising:providing a guidewire having proximal and distal ends, a proximal and adistal region, an expandable filter associated with the distal region,and a removable sheath which covers the expandable filter and isslidable over the guidewire; providing a balloon catheter having aninflatable balloon associated with a distal region of the ballooncatheter; introducing the distal end of the guidewire into the patient'svessel with the sheath covering the expandable filter, and positioningthe filter downstream of a treatment site, wherein the sheath andguidewire cross the treatment site; sliding the sheath toward theproximal end of the guidewire and removing the sheath from the vessel,wherein the expandable filter is uncovered; deploying the filter;advancing over the guidewire a balloon catheter to the treatment site;and inflating the balloon at the treatment site, wherein embolicmaterial is generated and captured before the expandable filter isremoved from the patient's vessel.
 2. The method of claim 1 wherein theexpandable filter includes a filter mesh.
 3. The method of claim 1wherein the filter is deployed before the balloon catheter is advancedover the guidewire.
 4. The method of claim 1 wherein the filter isdeployed after the balloon catheter is advanced over the guidewire. 5.The method of claim 1 wherein the filter is deployed before the balloonis inflated.
 6. The method of claim 4 wherein the filter is deployedbefore the balloon is inflated.
 7. A percutaneous system having filterand balloon catheter deployment capabilities, comprising: a guidewirehaving proximal and distal ends, a proximal and distal region, and anexpandable filter associated with the distal region; a sheath which isshaped to receive the guidewire and retain the filter in a contractedcondition, and to slidably release the filter to an expanded conditionwhen the sheath moves toward the proximal end of the guidewire; aballoon catheter having a proximal and a distal end, a proximal and adistal region, and a lumen which slidably receives the guidewire, theballoon catheter having an inflatable balloon associated with the distalregion, the balloon having a first diameter which permits intraluminaldelivery of the balloon catheter into a vessel, and having a secondexpanded diameter adapted to substantially engage a wall of the vessel;and wherein, during use, the guidewire is positioned across a region ofstenosis within the vessel, the filter is expanded, the balloon isinflated within the region of stenosis and wherein embolic material isgenerated and captured before the expandable filter is removed from thevessel.
 8. The system of claim 7 wherein the filter is self-expanding.9. The system of claim 7 wherein the filter comprises nitinol material.